Ovidiu Iordachi/Thinkstock(NEW YORK) -- You know it's really cold when they cancel school in Minnesota.

The last statewide school closure for freezing temperatures occurred in 1997 when temperatures plunged to 32 degrees below zero.

It estimated to get about the cold again on Monday with wind chills making it feel like it's minus 50 degrees.

Gov. Mark Dayton's decision to close all public schools from kindergarten through 12th grade will affect more than 800,000 Minnesota students.

The superintendent of one of Minnesota’s top-performing school districts, which oversees 3,000 students across four schools, said transportation is the biggest cause for concern in extreme weather, especially when it puts the safety of students in jeopardy.

“It’s the biggest thing that you worry about,” Mark Larson, superintendent of Mahtomedi School District, told ABC News. “It’s all about the students’ safety, getting them to school safely and getting them home safely.”

Meanwhile, school has also been cancelled for Milwaukee students on Monday and Chicago announced on Sunday that its public schools will be shut down on Monday as well.